Thermal characteristics of a volumetric solar absorption system

Solar volumetric heating is one of the alternative clean energy applications, and the improvement of thermal storage capacity of the system is necessary for the efficient applications. Consequently, volumetric solar absorption flow system incorporating the absorber plate in the channel was investigated for different Reynolds numbers and solar concentrations. The influence of the location of the absorbing plate on the heat transfer and hydrodynamic losses was also examined in the channel. In order to increase the thermal storage capacity of the working fluid, phase change materials of 7% concentration was incorporated in the analysis. Lauric acid was used as phase change materials, and water was considered as the carrier fluid in the channel. The performance and pump power loss parameters were introduced to assess the thermal performance of the volumetric solar absorption system. It is found that the performance parameter attained the highest value for the absorber plate location at the top of the channel, which was about 10% higher than those corresponding to the other locations. This was more pronounced with increasing Reynolds number and solar concentration. The pump power loss parameter was the highest for the absorber plate location at the mid‐height of the channel. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of optimum welding parameters in connecting high alloyed X53CrMnNiN219 and X45CrSi93 steels by friction welding

In this study, different welding parameters were applied to two different steels with high alloys and mechanical and metallographical investigations are performed. Thus, the optimum welding parameters were determined for these materials and working conditions. 12·30 diameter steel bars made up of 1·4871 (X53CrMnNiN219) and 1·4718 (X45CrSi93) steel were used as experimental material. The material loss increased with increase in friction and rotating pressure. No fracture at the welding region was observed and the highest fracture energy was identified in B5 group. Based on micro hardness investigation; the hardness profile reached its minimum value at the welding region.     

Investigation the effects of obstacle geometries and injection molding parameters on weld line strength using experimental and finite element methods in plastic injection molding

In this study, effects of injection parameters and weld line on the mechanical properties of polypropylene (PP) moldings were studied. To produce weld line at PP specimens, the obstacles having edge angle of 0°, 15° and 45° were designed. These obstacles were located at the center of the mold. The effects of both obstacles angles and the injection molding parameters such as melt temperature and packing pressure on the mechanical strength were investigated. Mechanical properties such as tensile strength and izod impact strength (notched) of the specimens were measured by test methods. The effect of molecular orientation on the mechanical properties of the specimens was discussed by Finite Element Analysis. Weld line tensile strength of injection molded specimens having obstacle edge angle (OEA) of 15° was obtained higher than the other obstacle edge angles.     

Ferromagnetic Behavior of Fe+ Implanted Si(100) Semiconductor

Fe ions have been implanted into Si (100) single crystals using ion implantation technique. The Fe ions have been accelerated to 45 keV with a dose of 5×10¹⁷ ion/cm² at room temperature. The ions have been sent to the substrate??s surface at normal incidence. The temperature dependence of magnetization measurement was explored at the temperature range of 10?C300 K. The implanted Si substrate was studied with Ferromagnetic Resonance (FMR) technique and Vibrating Sample Magnetometer (VSM). The FMR spectra were recorded by applying external magnetic field in different experimental geometries. FMR spectra were analyzed and the magnetic properties, which are the g-factor, effective magnetization and uniaxial anisotropy parameter, were estimated by simulation of the experimental data. The sample showed two-fold magnetic anisotropic symmetry. By fitting the Si-2p region obtained through XPS measurements it is observed that Fe and Fe compounds are present in the material.     

Selective and Sustainable Production of Sub-terminal Hydroxy Fatty Acids by a Self-Sufficient CYP102 Enzyme from Bacillus Amyloliquefaciens

Enzymatic hydroxylation of fatty acids by Cytochrome P450s (CYPs) offers an eco-friendly route to hydroxy fatty acids (HFAs), high-value oleochemicals with various applications in materials industry and with potential as bioactive compounds. However, instability and poor regioselectivity of CYPs are their main drawbacks. A newly discovered self-sufficient CYP102 enzyme, BAMF0695 from Bacillus amyloliquefaciens DSM 7, exhibits preference for hydroxylation of sub-terminal positions (ω-1, ω-2, and ω-3) of fatty acids. Our studies show that BAMF0695 has a broad temperature optimum (over 70 % of maximal enzymatic activity retained between 20 to 50 °C) and is highly thermostable (T₅₀ >50 °C), affording excellent adaptive compatibility for bioprocesses. We further demonstrate that BAMF0695 can utilize renewable microalgae lipid as a substrate feedstock for HFA production. Moreover, through extensive site-directed and site-saturation mutagenesis, we isolated variants with high regioselectivity, a rare property for CYPs that usually generate complex regioisomer mixtures. BAMF0695 mutants were able to generate a single HFA regiosiomer (ω-1 or ω-2) with selectivities from 75 % up to 91 %, using C12 to C18 fatty acids. Overall, our results demonstrate the potential of a recent CYP and its variants for sustainable and green production of high-value HFAs.     

A novel feature ranking algorithm for text classification: Brilliant probabilistic feature selector (BPFS)

Text classification (TC) is a very crucial task in this century of high-volume text datasets. Feature selection (FS) is one of the most important stages in TC studies. In the literature, numerous feature selection methods are recommended for TC. In the TC domain, filter-based FS methods are commonly utilized to select a more informative feature subsets. Each method uses a scoring system that is based on its algorithm to order the features. The classification process is then carried out by choosing the top-N features. However, each method's feature order is distinct from the others. Each method selects by giving the qualities that are critical to its algorithm a high score, but it does not select by giving the features that are unimportant a low value. In this paper, we proposed a novel filter-based FS method namely, brilliant probabilistic feature selector (BPFS), to assign a fair score and select informative features. While the BPFS method selects unique features, it also aims to select sparse features by assigning higher scores than common features. Extensive experimental studies using three effective classifiers decision tree (DT), support vector machines (SVM), and multinomial naive bayes (MNB) on four widely used datasets named Reuters-21,578, 20Newsgroup, Enron1, and Polarity with different characteristics demonstrate the success of the BPFS method. For feature dimensions, 20, 50, 100, 200, 500, and 1000 dimensions were used. The experimental results on different benchmark datasets show that the BPFS method is more successful than the well-known and recent FS methods according to Micro-F1 and Macro-F1 scores.     

Sesame seed as an alternative plant protein source: A comprehensive physicochemical characterisation study for alkaline,salt and enzyme-assisted extracted samples

Sesame seed is mostly utilised for its oil but also the waste of the oil processing; the seed meal has also significant potential to be used as an alternative protein source. In this study, the goal is to produce sesame seed protein by using three different techniques; alkaline, salt and enzyme-assisted extraction. A comprehensive physicochemical characterisation of the extracts was performed. Total and soluble protein contents, emulsification activity & emulsion stability, FTIR spectroscopy, hydration behaviour and gelling ability experiments by TD-NMR were conducted for all extracted proteins. Also, SDS-PAGE experiments were performed to observe the effect of extraction conditions on protein folding. Overall, the aqueous phase of enzyme-assisted extracted proteins (E-ACP) had the highest protein content and solubility, which resulted in other improved physicochemical properties. Salt extracted samples were ‘salted-out’, therefore, had poor physicochemical properties. TD-NMR experiments further confirmed the solubility and gelling ability results by measuring the change in the T₂ spin relaxation times. Additionally, FTIR spectroscopy confirmed the most critical peaks for the proteins; Amide I (C=O stretching) and Amide II (N–H bending). In summary, depending on the physicochemical property of interest, different extraction methods yielded proteins with different properties.     

Solar energy harvesting and self-cleaning of surfaces by an impacting water droplet

The self-cleaning of surfaces via impacting water droplets is examined pertinent to solar energy applications. The mechanism of spreading and retraction of the impacting droplet onto the dust and cleaned hydrophobic surfaces is considered in the analysis. The spreading factor of the impacting droplet is formulated incorporating the energy balance on the hydrophobic surface. High-speed photography is used to monitor the impacting droplet behavior. The functionalized silica particles coating is introduced towards generating hydrophobic wetting state on the glass surfaces. Environmental dust particles are characterized prior to self-cleaning impacting tests. It is found that spreading rate predicted for the impacting droplet agrees well with that obtained from the experiments. The droplet Weber number incorporated in the experiments does not result in droplet breaking on the surface upon impacting. The dusts are dissimilar in shapes and consist of several elements. Impacting droplet gives rise to cloaking of the dust on the surface during spreading and retraction. Almost all the dusts are removed from the surface through the impacting droplets; however, few dust residues are left on the impacting surface, which cover only 0.03% of the total surface area. Hence, we have demonstrated that self-cleaning of a surface can be achieved by an impacting droplet for renewable energy applications.     

The Effect of Different Polishing Sequences on the Adhesion of Streptococcus mutans to Feldspathic Porcelain

The aim of this research was to determine whether extra-oral surface treatments on feldspathic porcelain surfaces influence initial adhesion of Streptococcus mutans. Ninety-six porcelain specimen discs were fabricated and divided into six equal groups according to surface treatment: fine-grit diamond polishing (Group 1); self-glazing (Group 2); overglazing (Group 3); overglazing followed by a finishing procedure and then overglazing (Group 4); Pearl Surface polishing (Group 5); and Diamond Twist SCL^TM polishing (Group 6). Surface roughness and hydrophobicity were assessed. An S. mutans suspension was incubated on each specimen group and evaluated. A one-way analysis of variance, post-hoc Tukey honestly significantly different test, Friedman test, and t-test were used for statistical analysis. Group 1 showed the highest surface roughness (p < 0.001) and bacterial adhesion (p < 0.05). Groups 5 and 6 specimen surfaces presented significantly higher contact angles (p < 0.05). Group 1 had the highest S. mutans adhesion, followed by Groups 3, 5, 6, 2, and 4 (p < 0.05). Reglazing after grinding may therefore decrease bacterial adhesion beneficially.     

Influences of annealing temperature on anti-reflective performance of amorphous Ta2O5 thin films

Influences of thermal annealing on structural, optical and morphological properties of the tantalum pentoxide (Ta₂O₅) thin films were investigated and anti-reflective performances were discussed in detail. The Ta₂O₅ thin films were deposited onto Corning Glass (CG), Si, GaAs and Ge substrates by radio-frequency (RF) magnetron sputtering technique using Ta₂O₅ ceramic target. The obtained secondary ion mass spectroscopy (SIMS) analysis results showed that uniform Ta and O distribution have formed throughout depth of the films deposited on substrates. The X-Ray diffraction (XRD) results indicated that the annealed Ta₂O₅ thin films at 100, 200, 300 and 500?°C have exhibited amorphous (a-Ta₂O₅) characteristic. The increased temperature has resulted in increasing the surface roughness from 0.67 to 1.60?nm. The optical transmittance of the annealed thin films has increased from 70.85 to 80.32% with increasing temperature. Spectroscopic ellipsometer (SE) measurement results demonstrated that the increased temperature has increased the refractive index of the Ta₂O₅ thin film from 2.11 to 2.18. The Ta₂O₅ thin film has reduced the average optical reflectivity of the Si, GaAs and Ge substrates by 78, 55 and 70%, respectively. In addition, thermal annealing process has decreased the optical reflectivity of the film. The obtained experimental results showed that single-layer Ta₂O₅ thin films can be used as anti-reflective layer in optical and optoelectronic applications. The best optical transmittance and anti-reflective performance were obtained at the annealing temperature of 500?°C.